Amorphous carbon nanotube residue modification of solgel-synthesized C-, N-doped TiO 2 for photocatalytic applications
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RESEARCH PAPER
Amorphous carbon nanotube residue modification of solgel-synthesized C-, N-doped TiO2 for photocatalytic applications Sithembela A. Zikalala & Rengaraj Selvaraj & Faisal Al Marzouqi & Alex T. Kuvarega & Bhekie B. Mamba & Sabelo D. Mhlanga & Edward N. Nxumalo
Received: 30 June 2020 / Accepted: 16 November 2020 # Springer Nature B.V. 2020
Abstract The work reports an investigation into the role played by the carbon residue from low-quality amorphous carbon nanotubes (aCNTs) and nitrogen doped aCNTs (aNCNTs) in the properties of solgelsynthesized TiO2 and NTiO2. The resutant modified nanohybrids are compared to nitrogen-doped TiO2 where the N is sourced from an ethylenediamine as an organic C
This article is part of the topical collection: Nanotechnology Convergence in Africa Guest Editors: Mamadou Diallo, Abdessattar Abdelkefi, and Bhekie Mamba S. A. Zikalala : A. T. Kuvarega : B. B. Mamba : E. N. Nxumalo (*) Institute for Nanotechnology and Water Sustainability, College of Science, Engineering and Technology, University of South Africa, Johannesburg, Florida 1709, South Africa e-mail: [email protected] R. Selvaraj : F. Al Marzouqi Department of Chemistry, College of Science, Sultan Qaboos University, P.O. Box- 36, Al-Khoudh, P.C. 123 Muscat, Oman B. B. Mamba State Key Laboratory of Separation Membranes and Membrane Processes, National Centre for International Joint Research on Membrane Science and Technology, Tianjin 300387, People’s Republic of China S. D. Mhlanga SabiNano Research and Innovation Division (Inside MINTEK), Strijdom Park, Randburg, Johannesburg 2194, South Africa
and N precursor. The presence of carbon originating from ethylenediamine was confirmed by TGA and DTA while additional C doping originating from aCNT and aNCNT residues was confirmed by EDS and XRD spectroscopic techniques. XRD spectroscopy further demonstrated that the carbonaceous material residues resulted in the formation of TiC in TiO2–aCNT nanohybrids, and carbon nitride in NTiO2–aCNT nanohybrids. The TiC promoted photocatalytic performance of TiO2–aCNT nanohybrids while the carbon nitride residue increased charge recombination and thereby hampering the photocatalytic performance of NTiO2. A strong correlation exists between the optical properties and the photocatalytic performance in that NTiO2 has the lowest Eg (2.84 eV), second lowest charge recombination rate, and a high 2nd-order rate constant for the kinetics for CR dye removal. The TiO2–aCNT nanohybrids have the best overall performance in terms of dye adsorption, color removal through chemisorption, and UVA 254 TOC removal due to its low charge recombination. Therefore, the introduction of the carbonaceous materials into TiO2 significantly increases the adsorption capacity. Lastly, the presence of N in the carbonaceous materials further impedes the photocatalytic activity as observed by the low photocatalytic performance of NTiO2–aNCNT and TiO2– aNCNT nanohybrids. Keywords Solgel . Nanohybrids . Titania-amorphous carbon nanotube . Carbon doping . Nitrogen
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